MINNEAPOLIS — It is one of the great mysteries in recent American pop culture: the death of Prince almost one year ago and the circumstances that led him to be found crumpled on the floor of an elevator at his sprawling residence Paisley Park outside of Minneapolis.

How did he come into possession of the powerful opioid fentanyl, which killed him in what the coroner ruled was an accidental overdose? How did he so expertly conceal what appears to have been his addiction to pain medicines? And who, if anyone, bears some responsibility for his demise at 57?

To a surprising degree for a high-profile celebrity death, few answers have emerged for those questions. Many friends still seem at a loss to explain how a man who espoused a clean lifestyle, who had adopted a vegetarian diet and avoided marijuana and alcohol, could have hidden his dependency. Investigators continue their efforts but have given no indication they have discovered where Prince obtained the fentanyl.

This much is clear: Prince suffered from chronic hip pain, and that may have set him on a course to find relief. Surely, near the end, some of those closest to him understood that he had a drug problem. Six days before he died, his chartered jet had to make an emergency landing when he overdosed on a trip home from a concert, and plans were underway to have him see an addiction specialist.

But those efforts came too late to save Prince, whose departure left a huge void for fans, friends and those he had worked with.

“It’s a big hole,” said Van Jones, a political commentator and activist who was a friend of Prince’s. “I miss him a lot more than I thought I would. You never get past it. You could be sitting in your car, and all of a sudden a Prince song comes on, and you’re thinking about him again.”

Just a couple of weeks from the anniversary of his death, on April 21, here’s what is known about the various pieces of the mystery based on an array of recent interviews:

Investigators Still Mum

Pharmacy records. Doctors he saw. Friends.

There are only so many places investigators can look for information on how Prince may have acquired the fentanyl that killed him. But now those traps have been checked, no one has been arrested, and after a year, the going can get a bit tougher.

The investigation is being led by the Carver County Sheriff’s Office, in conjunction with the Drug Enforcement Administration. Jason Kamerud, chief deputy for the sheriff’s office, said that the findings would eventually be passed on to the United States attorney’s office, where a determination will be made on whether any prosecutions should be pursued.

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Sheriff Jim Olson of Carver County, Minn., taking questions from the media on the day following Prince’s death.CreditJim Mone/Associated Press

Typically in cases where the D.E.A. coordinates with local law enforcement, the agency focuses on doctors and pharmacies to see whether painkillers were improperly or illegally distributed to an individual. For its part, the sheriff’s office has, among other things, interviewed people who were at Paisley Park on the day Prince’s body was discovered, such as one doctor who was treating him but arrived too late.

As recently as February, the inquiry was active, according to a friend of Prince who was contacted at that time by a D.E.A. investigator.

If Prince’s fentanyl came from the black market — which appears clear, because investigators do not seem to have turned up a prescription — tracing it will be all the more difficult, as there is no official paper trail.

Once Focal, Now Largely Forgotten

In the days after Prince died, two doctors became figures in the drama.

One was Dr. Michael T. Schulenberg, who treated Prince before his death and arrived at the musician’s house on the day he died with test results, only to find him dead. Investigators questioned the doctor, who had prescribed an undisclosed medication to Prince, and executed a search warrant for the musician’s medical records.

The other was Dr. Howard Kornfeld, a California opioid addiction specialist, who had been called in by a friend of Prince to treat the musician for his dependency. Dr. Kornfeld’s son, Andrew, arrived at Paisley Park after Prince had died with a small dose of the drug Suboxone, an anti-addiction agent, which he was not legally authorized to administer.

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Dr. Michael T. Schulenberg, left, treated Prince before his death. Dr. Howard Kornfeld was preparing to take him on as a patient.

Today, neither the doctors nor Andrew Kornfeld seem to be of continuing interest to investigators.

Dr. Schulenberg, who left his post at North Memorial Health Care in the days following Prince’s death, is now employed at another clinic. He has not said what medication he prescribed for Prince, but there has been no indication from investigators that it was an opiate.

“Dr. Schulenberg has fully cooperated with the investigation,” his lawyer, Amy S. Conners, said in a statement. “He has had no further requests from any investigators following his voluntary interview with the Carver County Sheriff’s office on April 21, 2016.”

Dr. Kornfeld continues to run a treatment center in California, and his son is now applying to medical schools.

Dr. Kornfeld said in an interview that he is glad Andrew had the presence of mind to be the one who called 911 that morning, though Prince, it later turned out, had been dead for several hours. Andrew provided his own perspective in a first-person article for CNN’s website last year. “Believe me,” he wrote, “nothing can prepare a person to walk into such chaos and sadness.”

A Spotlight on Opioids

Prince’s death was just one in a surging number of fatal overdoses from opioids, which were a factor in some 33,000 deaths nationwide in 2015, the last year for which the Centers for Disease Control has statistics. Overdoses of opioids have quadrupled since 1999.

“Prince’s death has raised the profile of the opioid crisis even further,” said Dr. Chris Johnson, chairman of the Minnesota Department of Human Services Opioid Prescribing Work Group.

Minnesota officials said that fentanyl had not been seen on the local black market in appreciable numbers for some time. Then, last year, it became pervasive. Largely smuggled from labs in China and Mexico, fentanyl is significantly more potent than other opioids — as much as 50 times stronger than heroin. But it’s cheaper to produce, so it’s often disguised as more expensive prescription pain pills.

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A comparison of two potentially fatal dosages that demonstrates the potency of fentanyl versus heroin.Creditvia New Hampshire State Police Forensic Laboratory

Given that deception, said Kent Bailey, assistant special agent in charge at the Minneapolis office of the D.E.A., a vast majority of people who use fentanyl actually think they are taking something much milder.

Since Prince’s death, several regulatory changes have been approved, nationally, internationally and in his home state. The D.E.A., for example, decided in October to reduce by 25 percent the amount of opioids that could be manufactured in the United States. In August, Congress made it easier for doctors to prescribe two drugs that treat opioid dependence: buprenorphine and buprenorphine/naloxone, which is sold as Suboxone, and is the same drug Andrew had with him. In China, officials have agreed to ban the production of four types of fentanyl.

The broadest national response was passage of the Comprehensive Addiction and Recovery Act last summer, which authorized $181 million in spending to address the opioid epidemic. Minnesota officials enacted their own laws and regulations to address the problem, including requirements that doctors and pharmacists do a better job of tracking opioid prescriptions.

“Even though Prince’s final dose and exit was illicit,” Dr. Johnson said, “the reason he needed it was because of the years of prescriptions that got him on that path.”

Inside Paisley Park

Tours are now available of Paisley Park in Chanhassen, Minn., which its organizers describe as Prince’s “mythical creative sanctuary.” All manner of archives associated with his life are on view during the 70-minute tour (the $46 fee includes parking), but very little is said about his death.

Prince’s ashes are in his favorite room, the atrium, right near the entrance, kept in an urn designed as a miniature model of Paisley Park with the pop legend’s unpronounceable symbol, bejeweled and purple, on its front. The urn, housed in a frosted plastic encasement, is mounted high on a wall.

Prince spent a great deal of time in the atrium, according to the Paisley Park tour guide Mackenzie Timm. “He loved this space,” she said on a recent tour, pointing out the skylights that illuminate the space, the marble floor and the doves that live in two white cages on a mezzanine and occasionally coo. The room opens into a kitchen area, set up like a diner, with a big-screen TV where Prince liked to watch Minnesota Timberwolves and Minnesota Lynx games.

The elevator in which Prince died is not visible on the tour.

Estate ‘Mayhem’ Eases, but Disputes Persist

After a year that included business disputes, jockeying by consultants and outlandish claims of heirhood, the Prince estate has moved beyond what the judge in the case called a state of “personal and corporate mayhem.” But the estate, which could be worth up to $300 million, still has major issues to resolve and large tax payments to make.

Judge Kevin W. Eide has settled on six of Prince’s siblings and half-siblings as his likely heirs. He rejected claims from dozens of others, including one woman who said her marriage to Prince — who died without a will — had been kept secret by the C.I.A.

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Tyka Nelson, the sister of Prince, and her lawyers leaving the Carver County courthouse after a hearing last year on the musician’s estate.CreditAdam Bettcher/Getty Images

The estate includes $25 million in real estate holdings and, among other liquid assets, 67 gold bars. The value of Prince’s greatest asset — his vast music catalog, including unreleased material — is still undetermined, although the estate has struck a series of multimillion dollar deals to exploit it well into the future. The first big move, in February, was the return of Prince’s most popular songs to streaming services.

Those deals were made under the supervision of Bremer Trust, a Minnesota bank that was appointed special administrator shortly after Prince died. On Feb. 1, however, Comerica Bank & Trust took over as administrator, and the judge rejected efforts by two high-profile lawyers — L. Londell McMillan, who once represented Prince, and Van Jones, the CNN political commentator — to become personal representatives, a position similar to executor. Among other things, Judge Eide cited bitter disagreement about the qualifications of Mr. McMillan and Mr. Jones by the six presumptive heirs, who have split into two camps, four favoring Mr. McMillan and two favoring Mr. Jones.

In recent weeks, disputes among the heirs have continued, over legal fees and Comerica’s request for wider discretion in managing the estate.